The present invention relates to an arrangement structure of auxiliaries of an engine for a snow vehicle, such as a snow mobile.
Generally, in a front part of a vehicle body of a snow vehicle, such as a snow mobile, an engine is mounted in an engine room covered with an engine mount frame. In this engine, auxiliaries, such as an oil pump, an oil filter, and oil piping for supplying lubricating oil to respective parts of the engine, and a water pump and cooling water piping for supplying water to the engine, are arranged.
In an example of a related-art arrangement structure of auxiliaries of an engine for a snow vehicle, an exhaust manifold is arranged in a front upper part of an engine body, and an oil filter is disposed below the exhaust manifold so as to incline slightly forward in a vehicle traveling direction (refer to Patent Document 1). In another example, a supplying oil pump for supplying lubricating oil and a recovering oil pump for recovering the lubricating oil are arranged between a crank case and a magnet cover (refer to Patent Document 2). In still another example, a branch passage that leads to a relief valve disposed in an oil pan is provided in the middle of an oil passage communicating with an oil filter from an oil pump (refer to Patent Document 3).    Patent Document 1: Japanese Patent Publication No. 2003-41921 A    Patent Document 2: Japanese Patent Publication No. 2005-2940 A    Patent Document 3: Japanese Utility Model Publication No. 61-17204 A
However, in the related-art arrangement structures of the auxiliaries disclosed in the Patent Document 1, since the exhausted manifold, a water pump, and the like are arranged around the oil filter, it is difficult to create a sufficient maintenance space around the oil filter. Accordingly, it is difficult to perform replacement work of the oil filter.
In the related-art arrangement structure of the auxiliaries disclosed in the Patent Document 2, since a water pump is arranged in front of and above the crank shaft, the distance between the water pump and a heat exchanger arranged behind and below the engine becomes long, and consequently, the length of cooling water piping becomes large. For this reason, it is difficult to make an engine compact and light, and it is difficult to improve cooling efficiency.
Moreover, in this related-art arrangement structure of the auxiliaries, since the oil pump is arranged in front of and above the crank shaft, the distance between the oil pump and the lubricating oil within an oil pan arranged in a lower part of the engine becomes long, and consequently, an oil strainer becomes long, then the suction stroke of the lubricating oil extends. For this reason, it is difficult to increase the pumping efficiency of the lubricating oil. Therefore, an initial lubrication of the engine at the time of start of the engine might be delayed.
Furthermore, in the related-art arrangement structure of the auxiliaries disclosed in the Patent Document 3, an oil passage includes a vertical portion that is directed downward from a discharge port of an oil pump, a horizontal portion that connects lower end of vertical portion to the oil filter, and a branch passage that connects the middle of the horizontal portion to a lower oil pan. Accordingly, it is necessary to block the lower end of the vertical portion with a plug, or to provide an oil relief attaching seat with the branch portion. For this reason, it is necessary to take much time and cost for manufacturing the oil passage, and it is difficult to make the engine compact.
Moreover, in this related-art arrangement structure of the auxiliaries, the surplus oil from the oil pump drops to the horizontal portion of the oil passage. Therefore, bubbles are generated due to the dropped oil, and the surplus oil cannot be surely returned to the oil pump.